Thermostatically operated switch



June 21, 1949. e. w. CRIS E THERMOSTATICALLY OPERATED SWITCH Filed March 25, 1946 ('1'; "I'll VIIIIIII 'IIIIIIIIII INVENTOR. Geo/rye Wfrisc ATTORNEY.

Patented June 21, 1949 THERMOSTATICALLY OPERATED SWITCH George W. Crise, Columbus, Ohio, assignor to Crise Electric Manufacturing Company, Columbus, Ohio, a corporation of Ohio Application March 25, 1946, Serial No. 656,795

Claims. 1

My invention relates to thermostatically controlled switches and, more specifically, to thermostatic switches of the type employed in governing automatically the operation of electrical controls associated with heating, cooling, and other condition modifying systems.

In certain of its more specific aspects, m invention is concerned with thermostatic switches of the so-called snap-action type in which the circuit-completing contacts are maintained in relative engagement with the assistance of magnetic attraction supplied by a pair of permanent magnets. In mechanisms of this type, the magnetic field of attraction remains substantially constant when the contacts are in relative engagement so that the switch is responsive only to temperature differentials in overcoming the attraction of the magnets to permit of the separation of the contacts and open an associated circuit.

It is, therefore, an object of my invention to provide a snap-action switch in which the strength of the magnetic field between the magnets may be varied, whereby to increase or diminish the attraction forces between said magnets and thereby render the operation of the switch more sensitive to thermal conditions ambient thereto, such as in producing increased or decreased operating frequency of electricalapparatus associated with the switch in a given temperature cycle.

It is another object of my invention to provide a thermostatic switch in which the circuit completing contacts have their operation regulated by a pair of magnets, one of which being mounted on the deflectable end of a bimetallic element in a fixed position with respect thereto, and wherein the other element is adjustably mounted on a supporting member so that its operating positions may be varied to regulate the degree oi attraction exercised by said magnets on one another.

A further object of my invention is to provide in a switch of the character set forth, an adjustable magnet mounted on a screw threaded member and wherein the magnet carries a circuit contact whose operating positions are rendered adjustable in unison with said magnet by the screw threaded member.

It is still a further object of my invention to provide a thermostatic switch wherein the degree of snap-action may be varied, either at the factory or in the field, to adapt the switch for use with various electrical apparatus required for operating different degrees of snap-action.

It will be understood, that the term snapaction, as herein employed, is the sudden acceleration of the contact points of the thermostat into and out of engagement when the pull produced by an associated magnetic field either overcomes, or is overcome, by the spring tension of a bimetallic element.

For a further understanding of my invention. reference is made to the following description and appended drawings, wherein:

Fig. 1 is a front elevational view, partly in vertical section, of a thermostatic switch formed in accordance with the present invention;

Fig. 2 is a vertical transverse sectional view on the line 2-2 of Fig. 1;

Fig. .3 is a horizontal sectional view on the I line 3-3 of Fig. 1;

Fig. 4 is a tragmenta'ry perspective view of the adjustable magnet construction.

My invention makes use of a supporting base It) formed of an insulated material such as Bakelite, or other suitable plastics, and a casing ll substantially of the same material having an externally open aperture i2 through which an associated temperature dial may be viewed and operated.

The base it serves to rigidly support a tapered post l3 which in turn holds a bimetallic spiral element It at its outer end. The post I; also serves as one of the circuit terminals for the switch. A circular insulating bushing II is carried by the shaft portion of the post and serves as a bearing fora supporting bracket I! having a perpendicular flange I! at its upper portion.

A cam member I8 is rotatably supported upon the base by a pin l9 located above and substantially in axial. relation to the tapered post II. The cam carries a circular operating dial 2O having a suitably graduated scale substantially at its periphery, and: having its upper arcuate portion viewable through the aperture .l2. The dial 2!! is integrally cast with the cam member and serves as an externally located, manual operating means therefor.

The upper portion of the flange I1 is held in operating engagement with the cam member i 8 by a spring element 2i which has its upper end connected with the bracket I6, and its lower end rigidly held by a circular terminal bolt 2!.

The bimetallic spiral II is bentat its upper end to form a vertical arm which supports a permanent magnet 23. The magnet is rigidly fastened to the spiral by a pin extending laterally beyond the poles of the magnet to form a contact point 2|. A similar contact point 25 and another permanent magnet 26 are held in registration with the contact point 25 and the magnet ll by a threaded screw shaft 21. The shaft 21 is rotatably supported by a threaded aperture 2| located in the lower portion of the flange H. An adjustment handle 29 is connected with the outer end of the shaft 21 and serves as a manual control for the rotation of the shaft.

It will be understood, that as the shaft 21 and its attached magnet 26 are rotated, a. circular displacement of the magnetic field of the latter will take place, and the corresponding degree of attraction between the two magnets will be changed. To compensate for the variation in degree of attraction, the contact point 25 is moved longitudinally simultaneously with the rotation of the magnet to vary the spacing between the two contact points.

Assuming that my thermostatically operated switch is used to control the operation of the heating system, the bimetallic spiral l4 will be so constructed as to wind or rotate in a counterclockwise manner, as the temperature surrounding same rises.

, In operation, the desired temperature is set by moving the dial 20 to a given reading which in turn moves the flange and the screw shaft assembly, containing one of the contact elements of they-thermostat, to a relatively set position. If the temperature of the atmosphere surrounding the' bimetallic spiral is above the temperature setting on the dial, the contact points will normally be apart, resulting in an open circuit to the heating system. As the temperature decreases, the thermal action of the bimetallic spiral will gradually move the contact point 24 and the magnet 23 toward the opposite contact point 25 and its associated magnet 26. When the magnets are sufllciently close to one another,

the -magnetic attraction between the two will tom, the thermal action within the bimetallic spiral will tend to pull the contact points apart. However, the attraction forces of the magnets will continue to hold the contacts together until suillcient spring tension is built up within the spiral to overcome this force and snap the contacts'out of engagement. The resultant time to build up this tension necessarily allows the heating system to operate for a longer period than that required to reach the desired temperature setting of the dial. This condition, however, is a desirable one, and at present the majority of thermostats incorporate this feature, and are calibrated accordingly.

However, in different types of heating systems, it is desirable to control the degree of snapaction, as serious damage may result, in hot water heaters, for example, if the system is allowed a substantial over-run period. Therefore, my switch provides, by use of the rotatable magnet 2, a means for varying the degree of snapaction within the contact assembly. At the same e,'-the corresponding horizontal movement of its associated contact point 25 compensates for the calibration error produced by the variation in degree of attraction.

In view of the foregoing, it will be seen that my improved thermostatic switch may be adapted for use with numerous types of electrically operated conditioning mechanisms, by the simple adjustment of a single operating handle contained within the switch. While I have disclosed my thermostat as being used with a heating system, it will be understood that simple changes of the bimetallic element would render same operable with refrigeration or cooling systems wherein a variation of snap-action is desirable. My invention is characterized by its simplicity of construction, its operational efllciency and its economy of manufacture.

I claim:

1. In a thermostatic switch, a base, a bimetalli element mounted at one end on said base, said element having a free end deflectable in response to temperature variations, a contact carried by the free end of said element, a permanent magnet having spaced poles mounted on the free end of said element adjacent to said contact, an adjustable supporting member arranged on said base, a threaded device rotatably adjustable on said supporting member, a contact on one end of said device arranged for intermittent engagement with said element contact, and a second permanent magnet having spaced poles mounted on and bodily movable with said threaded device and disposed in registration with said first-named magnet, the rotational adjustment of said device causing variation in the strength of the magnetic field provided between said magnets and control of the spacing between said contacts.

2. In a thermostatic switch, a base, a bimetallic element mounted at one end on said base, said element having a free end deflectable in response to temperature variations, a contact carried by the free end of said element, a permanent magnet having spaced poles mounted on the free end of said element adjacent to said contact, an adjustable supporting member arranged on said base, a threaded device rotatably adjustable on said supporting member, a contact on one end of said device arranged for intermittent engagement with said element contact, a second permanent magnet having spaced poles mounted on and bodily movable with said threaded device and disposed in registration with said first-named magnet, the rotational adjustment of said device causing variation in the strength of the magnetic field provided between said magnets and control of the spacing between said contacts, and a rotatable cam in operating engagement with said supporting member, the rotation of said cam serving to move the supporting member and the device so as to vary the spacing between said contacts.

3. In a thermostatic switch, a base, a high resistance bimetallic element mounted at one end on said base, said element having a free end deflectable in response to temperature variations, a contact carried by the free end of said element, a permanent magnet having spaced poles mounted on the free end of said element ad- Jacent to said contact, an adjustable supporting member arranged on said base, a threaded device rotatably adjustable on said supporting member, a contact on one end of said device arranged for intermittent engagement with said element contact, and a second permanent magnet having spaced poles mounted on and bodily movable with said threaded device, the rotational adjustment of said device causing variation in the strength of the magnetic field provided between said magnets and control of the spacing between said contacts.

4. In a thermostatic switch, a base, a bimetallic spiral element mounted at one end on said base, said element having a free end deflectable in response to temperature variations, a contact carried by the free end of said element, a permanent magnet having spaced poles mounted on the free end of said element adjacent to said contact, an adjustable supporting member arranged on said base, a threaded device rotatably adjustable on said supporting member, a contact on one end of said device arranged for intermittent engagement with said element contact, and a second permanent magnet having spaced poles mounted on and bodily movable with said threaded device, the rotational adjustment of said device causing variation in the strength of the magnetic field provided between said magnets and control of the spacing between said contacts.

5. In a thermostatic switch, a base, a bimetallic element mounted at one end on said base; said element having a free end defiectable in response to temperature variations, a contact carried by the free end of said element, a permanent magnet having spaced poles mounted on the free end of said element adjacent to said contact, an adjustable supporting member arranged on said base, a threaded dc ice rotatably adjustable on said supporting member, a contact on one end of said device arranged for intermittent engagement with said element contact, a second permanent magnet having spaced poles mounted on and bodily movable with said threaded device, the rotational adjustment of said device causing variation in the strength of the magnetic field provided between said magnets and control of the spacing between said contacts, a rotatable cam in operating engagement with said supporting member, the rotation of said cam serving to move the supporting member and the device so as to vary the spacing between said contacts, and spring means connected with said supporting member serving to hold same in operating engagement with said cam.

GEORGE W. CRISE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,874,117 Persons Aug. 30, 1932 2,004,114 Hubbell June 11, 1935 2,323,910 Hubbell July 13, 1943 2,336,908 Winter Dec. 14,1943 

